Various approaches have been taken toward the development of electromechanical door locks which can be operated without the use of the key. Keyless door lock assemblies afford the user considerable convenience, and they eliminate the problems associated with lost and stolen keys.
One approach to the provision of an electrically powered door lock assembly is to employ a system in which the door bolt is actually driven by electrical power. Such electric strike door lock assemblies, however, must be powered directly from the building power, and accordingly they are expensive to install and usually must be mounted on the door frame, rather than the door itself.
Another approach has been to employ a battery-powered capacitor circuit which will release a surge of power to drive the motor or energize an electromagnet upon triggering of the circuit. Capacitor-based locks, however, have the disadvantage that they cannot be operated unless they are given sufficient time to recharge the capacitor. Moreover, maintaining the charge on the capacitor results in wasted energy that will shorten battery life.
Electromechanical locks which depend upon electrical power to move the bolt, or to move a lock releasing element, inherently face the problem that the mechanical parts can require significant energy to move. Thus, wear from general use, corrosion and shock from door slams can all result in binding or poor operation of the movable mechanical parts. Accordingly, the approach which is most suitable for a battery-powered lock assembly is for the user to manually move the movable mechanical elements in the assembly through manipulation of the door handle.
U.S. Pat. No. 4,457,148 to Johansson, et al. is typical of a structure employing an electromagnet assembly that is energized based upon a coded input. The user can manipulate the door handle to accomplish all three of: digital input to the electromagnet for energization of the same, closing of the armature in the electromagnet and movement of the locking member therewith, and movement of the bolt mechanism between the locked and unlocked position. The electromagnet power is employed solely to hold the locking element in a position which releases the bolt for movement. Power is not consumed to move the armature or to move the bolt.
One of the disadvantages of the approach taken in the lock disclosed in U.S. Pat. No. 4,457,148 to Johansson, et al. is that the door knob must first be rotated in one direction to close the air gap between the armature and the solenoid and then rotated in a second direction to open the lock. Moreover, input of the combination which activates the electromagnet is also accomplished by manipulating the handle in both directions. While one can easily learn this manipulation process, it is possible to become confused during the manipulating sequence, which can be particularly annoying if the result is that the combination must be re-input.
Accordingly, it is an object of the present invention to provide a battery-powered lock assembly and method in which movement of the mechanical parts is simplified and yet is powered by the user.
Another object of the present invention is to provide a keyless, electromechanical door lock assembly in which the movable armature of the electromagnet is held in a normally closed position eliminating the need to move the armature during opening of the lock.
A further object of the present invention is to provide a battery-powered lock assembly and method which is easier to use, can be opened by rotation of the door handle in either direction, is secure against attempts to open the lock without the proper combination input, is economical to manufacture and minimizes the electrical power required for operation.
Still another object of the present invention is to provide a battery-powered keyless electronic door lock assembly having an improved digital input means for energization of the electromagnet therein.
The battery-powered lock assembly and method of the present invention have other objects and features of advantage which will become apparent from and are set forth in more detail in the accompanying drawing and following description of the Best Mode Of Carrying Out The Invention.